Evaluate each of the following integral: `int_0^(pi//2)cos^2x\ dx`

Explanation

Consider `I=\int_{0}^{\pi / 2} \cos ^{2} x d x`


`I=\int_{0}^{\pi / 2} \cos ^{2}(\frac{\pi}{2}-x) d x \quad(\int_{0}^{a} f(x) d x=\int_{0}^{a} f(a-x) d x)`



`I=\int_{0}^{\pi / 2} \sin ^{2} x d x \quad \ldots \ldots(2)`


Adding 1 and 2, we get,
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